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American Water Raw Water Quality Not Textbook? Just Pilot! Iron Removal with High pH Raw Water March 27, 2008 Sandy Kutzing, P.E., CDM Eric Hahn, P.E., NJAW
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American Water Today’s Presentation u Background u Treatment Alternatives u Oxidation and Filtration u Fe and Water Chemistry u Pilot Test u Design
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American Water New Jersey American Water Current Operations u Serves more than 2 million people in 180 communities u 623,800 connections u 8,100 miles (12 000 km) of main from 2” to 72” (5 to 183 cm) in size u 170,000 valves, including hydrant branch valves
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American WaterBackground Monterey Beach, NJ u Existing well – PRM u Allocation limit of 900 GPM u SOS is limited on Barrier Island u Location u Large seasonal demand fluctuation
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American Water Project Location
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American Water Problem / Water Quality u Current Treatment u Sequestration u Customer Issues u Discoloration of laundry u Staining of sink u Taste and Odor
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American Water Iron Levels u Iron Requirement u NJDEP Secondary Contaminant – Recommended Upper Limit = 0.3 (mg/L) u With Sequestration Treatment – Recommended Upper Limit = 0.6 (mg/L) u When Upper limit is exceeded, Treatment must be added to reduce levels below 0.3 mg/L Monterey Well Iron Levels Year200220032004200520062007 Iron Levels (mg/L)0.90.7 1.00.8
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American Water Treatment Alternatives u Evaluated treatment methods u Membranes – eliminated due to space limitations and cost u Biological removal – eliminated due to increase in O&M u Oxidation with filtration – treatment method of choice
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American Water Oxidation with Filtration u Basics of treatment process u Oxidation of iron and manganese with the addition of chlorine u Dual media filtration of precipitates u Manganese dioxide coating on sand acts as catalyst for oxidation and reduction of iron and manganese
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American Water GreensandPlus Technology u Selected in previous study u GreensandPlus media u Silica sand u Manganese dioxide coating u Ordinary Manganese Greensand versus GreensandPlus
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American Water GREENSAND+
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American Water Existing Operations 1. Well Head 2. Tank (300K gal) 3. Booster Station 4. Discharge to Distribution System Chemical Injection
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American Water Location Details NJAW Monterey Well Site NJAW Vacant Lot
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American Water Proposed Site
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American Water Proposed Operations 2. GreensandPlus Filters 1. Well Head 3. Tank (300K gal) 4. Booster Station 5. Discharge to Distribution System Prechlorination Chemical Injection
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American Water Iron and Water Chemistry u Surface Water Iron u Oxidized form as precipitate u Typically removed by conventional clarification u Groundwater Iron u Deprived of Oxygen u Reduced Form (2+) and in solution
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American Water From “Water Treatment Handbook”, Degremont, 1979
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American Water Oxidation and Filtration u Most widely used treatment u Manganese Dioxide (MnO 2 ) or green sand u Oxidizes iron (II) and Manganese u Precipitated and retained by the filter media u Prechlorination oxidizes iron at Monterey Beach
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American Water Abnormal Water Quality and Filtration u Effectiveness varies with pH and oxidation-reduction potential (E H 2 ) u Monterey, NJ Well u Possibly collodial or complex iron u High pH (above 7.5) –Iron Fe 2+ (dissolved) most likely but not a guarantee
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American Water Iron: pH and Oxidation-Reduction Potential pH Potential (Volts)
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American Water
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Bench Scale Test u Prechlorinate to oxidize iron u Filter u Test for removal of Iron u Confirm: Iron form likely Fe 2+
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American Water Pilot Test u Higher Loading Rates u 5 to 7 gpm/ft 2 u Confirm Iron and Manganese Removal u Prechlorinate u Impact of MnO 2 coated green sands
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American Water Pilot Study
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American Water Pilot Study Results u Effluent Iron concentrations u 0.05 mg/L u Effluent Manganese concentrations u 0.02 mg/L u Headloss
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American Water Pilot Study Results Iron (mg/L) Filter Run Time (Hours) 10204060305070 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Raw, 5 gpm/sf Raw, 7 gpm/sf Effluent, 5 gpm/sf Effluent, 7 gpm/sf NJDEP Secondary Contaminant Level NJAW Performance Requirement
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American Water Pilot Study Frequency Effluent Iron Concentration
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American WaterDesign u GreensandPlus filters u Regular operation u Backwash operation (one filter backwashing) u Benefits of higher loading rate u Recycle 85% backwash flow
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American WaterRecap u Background u Treatment Alternatives u Oxidation and Filtration u Fe and Water Chemistry u Bench Scale & Pilot Tests u Design Questions?
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